In passenger aircraft there are competing considerations related to passenger seats and seat support structure. Foremost is passenger satiety in the event that high g forces are experienced. The seat must maintain its integrity at moderate g forces unlikely to result in passenger injury, but the situation is more complicated than simply providing a strong seat and support structure. At higher g forces, an unyielding seat is more likely to cause injury than a seat which will flex, bend or collapse in a controlled manner. The situation is further complicated by the fact that sudden breaking of a seat support can result in a dangerous rapid increase in g forces, in addition to increasing the likelihood of puncture injury to passengers or the aircraft by the broken support pieces. Therefore, modern government regulations provide limits within which seat supports must not permanently yield (i.e., moderate g forces) and higher limits within which the seat supports can yield but not fail.
Other important considerations are space and weight. Passenger seats and seat frames must be both compact and light. For example, the space under the seat must be as open as possible in order to accommodate the feet and lower legs of passengers of the next row and, traditionally, carry-on luggage. As a result, conventional seat frames have narrow upright support members. Early versions of such frames used a plurality of tubular members connected by braces and brackets. Newer seat frames have one-piece upright supports machined or cast of solid metal with carefully positioned voids and areas of reduced thickness to decrease weight while maintaining adequate strength and performance over the required range of g forces.
Another consideration in aircraft passenger seating has been passenger comfort which, recently, has been considered to be related to passenger entertainment. It now has been proposed that more interactive electronic systems be provided for individual passengers. Sophistication of electronics proposed for each seat continues to increase. Such electronics require control systems and power supplies that generate heat. In standard seat constructions there is no convenient location for an additional, sometimes fragile, unit which may become hot. Space is at such a premium that almost any additional unit of any substantial size will be exposed or adjacent to a passenger. Heat-generating components have been encased in housings mounted on the seat support structure at vulnerable locations. The housings have been insulated to avoid inconveniencing the nearest passengers. Power consumption must necessarily be low to avoid heat buildup within the housings that could damage the electronics. Low power consumption also is required in order to avoid uncomfortable hot spots close to passengers. Routing of wires to and from such units also has been a problem.